Importance and functions of aluminium alloys
The properties of aluminium depend on a whole range of factors. The other elements that are present in commonly used alloys, either as deliberate additions or as impurities, play a particularly important role.
With the exception of refined aluminium (Al99,99), the aluminium used on a commercial scale is always in the form of an aluminium alloy containing additional elements. Unalloyed or very weakly alloyed aluminium is mainly used to produce foil and strip, chemical equipment and products for electronic and electrical engineering applications.
The purpose of alloying is to improve the properties of aluminium, especially strength – most unalloyed metals are soft – and corrosion resistance.
The main alloying elements used with aluminium are copper (Cu), silicon (Si), magnesium (Mg), zinc (Zn) and manganese (Mn).); lead, boron, chromium, nickel, titanium, bismuth and zirconium are also used in small quantities. When only present in quantities of a few per cent, or even fractions thereof, each of these elements improves certain properties of aluminium, often at the expense of other properties so that another element has to be added to cancel out this detrimental effect.
Aluminium alloys are produced by melting, sintering (manufacture of shaped parts using metal powder that is fused together at elevated temperatures) or mechanical mixing. One differentiates between casting alloys and wrought alloys depending on the how the alloys are intended to be processed further.